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ABSTRACT Heteroepitaxial thin films of Ba0.7Sr0.3TiO3 (BST-0.3) solid solutions were grown on single-crystal (001) MgO substrates by high-frequency cathode sputtering of a stoichiometric ceramic target. The parameters of the tetragonal... more
ABSTRACT Heteroepitaxial thin films of Ba0.7Sr0.3TiO3 (BST-0.3) solid solutions were grown on single-crystal (001) MgO substrates by high-frequency cathode sputtering of a stoichiometric ceramic target. The parameters of the tetragonal unit cell of a film were determined by x-ray diffraction methods, and the temperature dependence of the parameter c was studied depending on the synthesis conditions in the temperature range 293–520 K. An E(TO) soft mode was observed in the Raman spectra, the frequency of which correlates with two-dimensional stresses arising in films. It is shown that the two-dimensional stresses in a film are controlled not only by the film-substrate lattice constant mismatch and the difference of their thermal expansion coefficients but also are significantly dependent on the heteroepitaxial growth mechanism. It is shown that the phase transition to the tetragonal paraelectric phase during film heating occurs irrespective of the growth mechanism.
Research Interests: Condensed Matter Physics, Materials Science, Quantum Physics, Solid State Physics, High Frequency, and 15 moreStrontium, Thin Film, BARIUM TITANATE, Phase transition, Barium strontium titanate, Temperature Dependence, Lattice Dynamics, Thermoelastic Damping, X ray diffraction, Single Crystal, Strontium Titanate, Raman Spectra, Linear Coefficient of Thermal Expansion, Solid Solution, and Growth mechanism
A Nd-doped BiFeO(3) thin film deposited on MgO substrate was studied by synchrotron diffraction. The ferroelectric nature of the film is proven by in-plane remanent polarization measurement. The highest possible symmetry of the film is... more
A Nd-doped BiFeO(3) thin film deposited on MgO substrate was studied by synchrotron diffraction. The ferroelectric nature of the film is proven by in-plane remanent polarization measurement. The highest possible symmetry of the film is determined to be orthorhombic, within the Fm2m space group. Such a structure is rotated by 45° with respect to the substrate and is consistent with tilts of oxygen octahedra doubling the unit cell. This polar structure presents a rather unusual strain-accommodation mechanism.
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The water footprint has been introduced as a potential sustainability indicator for human-induced water consumption, and has frequently been studied at local, national and international scales during the last decade. While water... more
The water footprint has been introduced as a potential sustainability indicator for human-induced water consumption, and has frequently been studied at local, national and international scales during the last decade. While water footprints are sometimes understood as a measure that includes environmental impact assessment, the water footprint as used in this paper refers to volumes of water consumed, without including weighting procedures to allow for the assessment of impacts. Two types of approaches have been applied to calculate the water footprint in the literature: bottom-up and top-down approaches. This study compares and discusses advantages and limitations of the water footprint of nations based on two input–output top-down approaches (Water Embodied in Bilateral Trade (WEBT) and Multi-regional Input–Output Analysis (MRIO)) and of the existing national water footprint accounts from the literature based on the bottom-up approach. The differences in the bottom-up and WEBT approaches are caused by inter-sectoral cut-off, because bottom-up approaches do not consider the entire industrial supply chains, while the WEBT method covers the water footprint by tracing the whole domestic supply chain of each country. The differences in the WEBT and MRIO approaches are due to an inter-regional cut-off effect, as the WEBT approach only traces domestic supply chains whereas the MRIO approach traces entire global supply chains. We found that both bottom-up and top-down approaches are heavily dependent on the quality of existing datasets, and differ substantially. The total water footprints of nations based on different approaches vary by up to 48%, and this variation is even larger at the sector level.
Research Interests: Environmental Science, Natural Resources, Consumption, Environmental Impact Assessment, Supply Chain, and 15 moreEnvironmental Impacts, Resources, Ecological Footprint, Environmental Impact, Hybrid Approach, Footprint, Natural Resource, Bilateral trade, Economic systems, Life Cycle Analysis, Input Output, Bottom Up, Global Supply Chain, Sustainability, and Sustainability Indicator
Pt/graphene electrocatalyst for fuel elements has been obtained via the simultaneously electrochemical dispersion of Pt foil and expanded graphite by applying the alternating current. Raman spectroscopy and transmission electron... more
Pt/graphene electrocatalyst for fuel elements has been obtained via the simultaneously electrochemical dispersion of Pt foil and expanded graphite by applying the alternating current. Raman spectroscopy and transmission electron microscopy (TEM) have revealed multilayered structure of graphene (3-5 layers) with linear defects of graphene sheets near 1 μm. The microstructural characteristics and catalytic activity of synthesized Pt/graphene catalyst have been compared with those of Pt/Vulcan catalyst prepared under the same conditions. Pt nanoparticles of Pt/Graphene catalyst exhibit smaller average dimensions and narrower particle size distribution. It follows from the electrochemical study that the electrochemical surface area of Pt/graphene catalyst is 2.5 times higher than for Pt/Vulcan. Besides this, the activity in the electrooxidation of methanol and the stability of Pt/graphene catalyst are found to be superior to the analogous parameters of Pt/Vulcan specimen.
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The present work is aimed at calculating the intensities of the intrinsic T2g band through an UO2 ceramic surface using electron back-scattering diffraction data. The theoretical intensity distribution is displayed in the form of a... more
The present work is aimed at calculating the intensities of the intrinsic T2g band through an UO2 ceramic surface using electron back-scattering diffraction data. The theoretical intensity distribution is displayed in the form of a color-scale image and compared with an experimental Raman imaging map to establish circumstances of the T2g intensity variation within the UO2 ceramic surface and to determine the crystalline orientations. The results evidence a quite good coincidence between theory and experiment, although some grains highlight pronounced differences in T2g intensities for both maps. One therefore implies other “side” effects which make contribution to the T2g intensity behavior within a UO2 ceramic surface, such as different penetration depths of exciting beams in EBSD and Raman spectroscopy, or local stoichiometric changes.The present work is aimed at calculating the intensities of the intrinsic T2g band through an UO2 ceramic surface using electron back-scattering diffraction data. The theoretical intensity distribution is displayed in the form of a color-scale image and compared with an experimental Raman imaging map to establish circumstances of the T2g intensity variation within the UO2 ceramic surface and to determine the crystalline orientations. The results evidence a quite good coincidence between theory and experiment, although some grains highlight pronounced differences in T2g intensities for both maps. One therefore implies other “side” effects which make contribution to the T2g intensity behavior within a UO2 ceramic surface, such as different penetration depths of exciting beams in EBSD and Raman spectroscopy, or local stoichiometric changes.
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Abstract Copper oxide powders (CuOx) were reported to be electrochemically obtained under pulse alternating current by a facile and inexpensive one-pot method. The effect of the synthesis conditions on the copper electrode oxidation rate... more
Abstract Copper oxide powders (CuOx) were reported to be electrochemically obtained under pulse alternating current by a facile and inexpensive one-pot method. The effect of the synthesis conditions on the copper electrode oxidation rate and product morphology and composition was studied. The CuOx products were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Depending on the synthesis conditions, the powders reveal different morphologies and composition, such as Cu2O octahedra, Cu2O decorated with CuO or Cu2O-CuO bilayered composite. Cyclic voltammetry and charge-discharge measurements were used to study the electrochemical energy conversion properties of the materials. The results of the electrocatalytic study indicate that the powder with Cu2O-CuO bilayered polyhedra is suitable for use in methanol oxidation; and the powder with Cu2O octahedra has shown a good specific capacitance for supercapacitors.
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ABSTRACT
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ABSTRACT The Gd3+ ESR spectrum of the antiferroelectric phase of a PbZrO3 single crystal contains at least one pair of magnetically equivalent components. The angular dependences of the resonance magnetic field that were constructed for... more
ABSTRACT The Gd3+ ESR spectrum of the antiferroelectric phase of a PbZrO3 single crystal contains at least one pair of magnetically equivalent components. The angular dependences of the resonance magnetic field that were constructed for them transform into one another by mirror reflection in a plane perpendicular to the antipolarization axis of the crystal. The constants in the spin Hamiltonians for the corresponding pair of paramagnetic centers are determined assuming monoclinic symmetry. (C) 1999 American Institute of Physics. [S1063-7834(99)03207-4].
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The authors extend their previous work published in Leontyev and TachiyaJ. Chem. Phys. 123, 224502 (2005) and study not only forward but also reverse electron transfer between pyrene and dimethylaniline in a nonpolar solvent, n-hexane.... more
The authors extend their previous work published in Leontyev and TachiyaJ. Chem. Phys. 123, 224502 (2005) and study not only forward but also reverse electron transfer between pyrene and dimethylaniline in a nonpolar solvent, n-hexane. The distribution function methodology and molecular dynamics technique adopted in their previous work are used. Two algorithms (I and II) are formulated for obtaining the reorganization energy and the solvation free energy difference in the linear response approximation. The two algorithms are combined with different cutoff schemes and tested for polarizable and nonpolarizable solvent models. Agreement between the results obtained by the two algorithms was achieved only for simulations employing the particle mesh Ewald treatment. It is concluded that algorithm I provides a reliable scheme for evaluation of the reorganization energy and the solvation free energy difference. Moreover, a new algorithm referred to as the G-function algorithm is formulated which does not assume the linear response approximation, and is tested on evaluation of the solvation free energy difference. Agreement between the results from the G-function algorithm and those from algorithms I and II is fairly good, although it depends on the degree of statistical consistency of the simulations. In the case of nonpolar solvents the G-function method has practical importance because, unlike the conventional thermodynamic integration approach, it requires equilibrium molecular configuration ensembles only for the initial and final states of the system.
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The intermolecular electron transfer in a solute pair consisting of pyrene and dimethylaniline is investigated in a nonpolar solvent, n-hexane. The earlier elaborated approach [M. Tachiya, J. Phys Chem. 97, 5911 (1993)] is used; this... more
The intermolecular electron transfer in a solute pair consisting of pyrene and dimethylaniline is investigated in a nonpolar solvent, n-hexane. The earlier elaborated approach [M. Tachiya, J. Phys Chem. 97, 5911 (1993)] is used; this method provides a physically relevant background for separating inertial and inertialess polarization responses for both nonpolarizable and polarizable molecular level simulations. The molecular-dynamics technique was implemented for obtaining the equilibrium ensemble of solvent configurations. The nonpolar solvent, n-hexane, was treated in terms of OPLS-AA parametrization. Solute Lennard-Jones parameters were taken from the same parametrization. Solute charge distributions of the initial and final states were determined using ab initio level [HF/6-31G(d,p)] quantum-chemical calculations. Configuration analysis was performed explicitly taking into account the anisotropic polarizability of n-hexane. It is shown that the Gaussian law well describes calculated distribution functions of the solvent coordinate, therefore, the rate constant of the ET reaction can be characterized by the reorganization energy. Evaluated values of the reorganization energies are in a range of 0.03-0.11 eV and significant contribution (more then 40% of magnitude) comes from anisotropic polarizability. Investigation of the reorganization energy lambda dependence on the solute pair separation distance d revealed unexpected behavior. The dependence has a very sharp peak at the distance d=7 A where solvent molecules are able to penetrate into the intermediate space between the solute pair. The reason for such behavior is clarified. This new effect has a purely molecular origin and cannot be described within conventional continuum solvent models.